Method op forming partly foamed plastic articles

ABSTRACT

8. IN A PROCESS FOR THE PRODUCTION OF BLOW MOLDED HOLLOW PLASTIC ARTICLES WHEREIN A PARISON OF SAID PLASTIC IS FORMED AND THEN SAID PARISON IS EXPANDED WITHIN A MOLD TO CONFORM TO THE CONTOUR OF SAID MOLD BY A FLUID MEDIUM, THE IMPROVEMENT COMPRISING INCORPORATING A FOAMING AGENT INTO SAID PLASTIC PRIOR TO FORMATION OF SAID PARISON SO THAT SAID PARSION IS FOAMED BEFORE BEING MOLDED, THEREBY FORMING A FOAMED PLASTIC ARTICLE AS A PRODUCT OF THE PROCESS.

Sept. 26, 1972 T. R. SANTELLI Re. 27,484

METHOD OF FORMING PARTLY FOAMED PLASTIC ARTICLES Original Filed Oct. 19.1959 5 Sheets-Sheet 1 Lzg.

ATTORNEY Sept. 26, 1 972 T. R. SANTELLI METHOD OF FORMING PARTLY FOAMEDPLASTIC ARTICLES Original Filed Oct. 19, 1959 5 Sheets-Sheet mm? TL Y muV N mm x 0 m R r A sfl A 2% w .m

w 4 L1 Zia/2,91%

V A a f Sept. 26, 1972 T. R. SANTELL! I 27,484

METHOD OF FORMING PARTLY 'FOAMED PLASTIC ARTICLES Original Filed Oct.19, 1959 s Sheets-Sheet 3 INVENTOR.

mm; R. SANTELL! BY M%. W;

ATTORNEY Sept. 26, 1972 T. R. SANTELLI METHOD OF FORMING PARTLY FOAMEDPLASTIC ARTICLES 5 Sheets-Sheet 4 Original Filed Oct. 19 1959 a 1 x, w vA 'l/I/I/I/I THOMAS R. Snnrrnu ATTORNEY wnwgwz METHOD OF FORMING PARTLYFOAMED PLASTIC ARTICLES ginal Filed Oct. 19 1959 Sept. 26, 1972 T. R.SANTELLI 5 Sheets-Sheet 5 Ori .mi mm N 5 NA .N 15 MR a w 3% Z UnitedStates Patent Office Re. 27,484 Reissued Sept. 26, 1972 27,484 METHOD OFFORMING PARTLY FOAMED PLASTIC ARTICLES Thomas R. Santelli, Sylvania,Ohio, assignor to Owens-Illinois, Inc.

Original No. 3,144,493, dated Aug. 11, 1964, Ser. No. 847,144, Oct. 19,1959. Application for reissue June 30, 1966, Ser. No. 569,764

Int. Cl. B29c 17/07; B29d 27/00 US. Cl. 264-45 16 Claims Matter enclosedin heavy brackets II] appears in the original patent but forms no partof this reissue specification; matter printed in italics indicates theadditions made by reissue.

This invention relates to plastic articles having an end portion insubstantiall unexpanded or unfoarned condition with the balance of thearticle being integral therewith and in expanded or foamed condition. Inanother aspect the invention relates to a method for forming such anarticle.

Various articles made of foamed or cellular plastics are desirablebecause of the various unique properties of foamed plastics, such ascushioning and insulating effects or because of the savings in materialwhich can be realized when producing the article from a plastic incellular form. However, it has not been desirable to form many objectsfrom cellular plastics in the past because some objects require greaterstrength or rigidity in certain areas or portions than can be oifered bythe particular cellular plastic in question.

It is, therefore, an object of the invention to provide a method offorming a cellular plastic article having an end portion which is in asubstantially unexpanded condition and integral with the cellularportion of the plastic article.

It is another object of the invention to provide a method for producingsuch an article.

Other objects and advantages of the invention will be come apparent froma consideration of the accompanying disclosure and the drawings.

According to the invention there is provided a method which comprisesproviding a quantity of hot plasticized plastic material containing anintimately dispersed foaming or cellulating agent, forming asubstantially unexpanded, non-cellular shaped end portion of an articlefrom a portion of said plastic material under shaping conditions whichprevent any substantial foaming of said portion by said foaming agent,from another portion of said quantity of plastic material forming thebalance of said article integral with said shaped end portion underconditions whereby said second portion of said article is expanded intoa cellular structure by the action of said foaming agent.

Further according to the invention there is provided a method forforming a plastic article having a cellular portion integral with an endportion formed from the same plastic composition as said cellularportion, said end portion being in a substantially solid or unexpanded,noncellular-condition.

Blowing or foaming agents which are dispersed in plastics are of twomain general types. In the first type the blowing agent is a chemicalblowing agent, that is, one which evolves a gas under the influence ofheat by chemical reaction or chemical decomposition. The second type ofblowing agent is a physical blowing agent, such as a volatile liquiddispersed in the plastic, such liquid forming a gas or vapor under theinfluence of elevated temperatures and/or lowered pressures. Suchfoaming agents are well known and will not be discussed in detail here.Either type of blowing agent is applicable in the present invention.

Chemical foaming agents are usually employed at a concentration of fromabout 0.5 to weight percent of the plastic composition, including thefoaming agent, although higher or lower amounts are applicable.

The nature of the invention will be better understood from a descriptionof the drawings which illustrate several suitable types of apparatus forcarrying out the method and producing the article of the invention.

Referring to accompanying drawings:

FIGS. 1 through 6 inclusive are sectional elevational views of onesuitable apparatus for performing the method, showing the parts indifferent positions corresponding to various steps of the method;

FIGS. 7 through 10 and I3, 14 and 15 inclusive are sectional elevationalviews of another apparatus for performing the method, showing the partsin difiierent positions corresponding to the various steps in themethod;

FIG. 11. is a sectional view at the line 11l1 of FIG. 9-

FIG. 12 is a sectional view of the line 12-12 of FIG. 7; and

FIGS. 16, 17 and 18 illustrate sectional views of another apparatussuitable for effecting the method of the invention showing the parts indilferent positions.

As shown in FIGS. 1 through 6, an apparatus for performing the methodincludes a body 20 having a vertical opening therethrough and an orificering 21 overlying the vertical opening. A mandrel 22 is positioned inthe opening thereby forming a tubular cavity 23. The tubular cavity 23is in communication with the outlet of a plasticizer and extruder (notshown) through a channel 24.

A sleeve 25 surrounds the mandrel 22 and is reciprocable by means (notshown) from a position above and overlying the channel 24 to a lowerposition whereby the tubular cavity 23 can be brought into and out ofcommunication with the channel 24.

A partible neck mold 26 and a hollow core 27 are mounted above the body20 for axial movement into and out of alignment with the open end of thecavity 23. A partible finishing mold 28 (FIGS. 5 and 6) is provided forexpanding the plastic tube to finished form, as hereinafter described.The bottom of the mold sections are beveled at 29 and spaced apart at 30in order to pinch the plastic material and seal the end thereof.

At the beginning of the operation of the apparatus shown in FIGS. 1through 6, a quantity of hot plastic containing foaming agent materialand sufiicient to fill the tubular cavity is introduced from the sourceof plastic through the channel 24 to the cavity. The mass of plasticmaterial in the tubular cavity is isolated from the parent mass ofplastic material by movement of the sleeve 25 upwardly across thechannel 24. The apparatus if then in position for the beginning of thecycle and the neck mold 26 is brought into contact with the body 20, thecore 27 contacting the mandrel 22 (FIG. 1).

The sleeve 25 is then moved upwardly under controlled pressure asufficient distance to force a portion of the plastic material in thetubular cavity upwardly in order to fill the neck mold 26 and form thefinish or end portion of the article (FIG. 2). The sleeve 25 is thenretracted downwardly to reestablish communication with the plasticmaterial (FIG. 3). Simultaneously the neck mold is moved upwardly andaxially away from the end of the cavity. The pressure of plasticmaterial from the parent mass forces plastic material into the tubularcavity, and prevents any substantial expansion by foaming of the plasticin the neck mold. Also, the mold chills the plastic sufficiently thatexpansion is avoided when the neck mold is later removed. A portion ofthe plastic material in the cavity 23 is displaced out of the open endof the cavity, thereby forming a length of tubing integral with theneck. As this tubing is formed the foaming agent therein causesexpansion into a tube of foamed or cellular plastic as it issues fromthe cavity. As the desired length of tubing is formed, the sleeve isagain moved upwardly to cut off or resegregate the parent mass from theplastic material in the tubular cavity. A shear blade 31 is then movedacross the orifice to sever the length of tubing from the plasticmaterial in the tubular cavity (FIG. 4).

The sections of the hollow mold 28 may then be closed about the plasticmaterial, thereby pinching the lower end of the tubing. The foamedtubing can then be expanded to the confines of the mold by applyingfluid under pressure through the hollow core 27 (FIGS. 5 and 6).

After the tubing has been severed from the plastic material in thecavity (FIG. 4), the apparatus is again in position for beginning thecycle by bringing a neck mold into contact with the body 20 and formingthe neck finish by moving the sleeve 25 upwardly. 1

A modification of the method can be performed by retracting the sleeve25 at the beginning of the cycle as shown in FIG. 5a to permit a limitedquantity of plastic to enter the tubular cavity and then moving thesleeve upwardly, simultaneously isolating the quantity of plastic in thetubular cavity and forcing plastic into the neck mold positioned overthe cavity as shown by FIGS. 2 and 8. The sleeve is then retracted andthe neck mold moved axially away from the cavity to form a length oftubing integral with the neck, in the same manner as heretoforedescribed. As the desired length of tubing is formed the sleeve is againmoved upwardly as in FIG. 4, or rotated as in FIG. to isolate orresegregate the plastic material in the cavity and the length of tubingis severed. The cycle of operations can then again be started by theretraction of the sleeve. 7

Another apparatus for performing the method is shown in FIGS. 7 through15, inclusive. In this apparatus the sleeve 25' is provided with a slotor groove 32 extending longitudinally along the outer surface of thesleeve to the upper end thereof. In the operation of this apparatus thetubular cavity is initially filled with plastic material containingfoaming agent as in the form of the apparatus shown in FIGS. 1 through6. The sleeve 25 is in the position shown in FIG. 7 wherein the plasticmaterial in the tubular cavity is isolated or segregated fromcommunication with the parent mass and the groove 32 is in a positionout of communication with the channel 24 (FIG. 12.) The sleeve 25' isthen moved upwardly to force plastic material into the neck mold,thereby forming the neck finish (FIG. 8). The sleeve is then rotated tobring the groove 32 into communication with the channel 24, therebypermitting plastic material to flow from the parent mass to the tubularcavity (FIGS. 9, l1). Simultaneously with this action, the neck mold ismoved axially away from the cavity, thereby forming a length of tubingintegral with the neck finish by the flow of plastic material out of thetubular cavity. During the forming of the tubing the sleeve is retractedinto its lower position. As the desired length of tubing is formed, thesleeve is again rotated to bring the groove 32 out of register with thechannel 24 isolating or resegregating the plastic material in the cavityfrom the parent mass (FIG. 10).

The neck finish and integral tubing can then be severed (FIG. 10) andsealed and expanded, as shown in FIGS. 13 and 14, by closing the moldsections and supplying fluid under pressure through the core.

At the severing of the tube from the material in the tubular cavity, thevarious parts are again in position for application of pressure to themass of plastic in the tubular cavity to force plastic out of thetubular cavity and once again begin the cycle of forming a hollowplastic container.

In FIGS. 16, 17 and 18 there is illustrated another method for making asomewhat different article according to the invention. This specificarticle illustrated is a solid, substantially unfoamed bottle cap havinga central plug portion in foamed condition. The illustrated apparatusincludes a body 34 having a vertical opening therethrough and an orifice35 overlying the vertical opening. The vertical opening 36 is incommunication with the outlet of a plasticizer and extruder (not shown)through a channel 37. A plunger 38 is positioned in opening 36 and isreciprocable by means (not shown) from a position well above opening 35,such as the position shown in FIG. 17 to a lower position, such as shownin FIG. 16, whereby the opening 36 can be brought in and out ofcommunication with orifice 35.

A particle mold 33 is mounted above the body 34 for axial movement intoand out of alignment with the orifice 35.

At the beginning of the operation of the apparatus shown in FIGS. 16through 18, the respective parts of the apparatus are as shown in FIG.18, except that the mold 33 contains no plastic. A quantity of plasticcontaining foaming agent has already been introduced into opening 36through the channel 37 as shown in FIG. 18. The mold is moved intoalignment with orifice 35 so as to close the apparatus and the plunger38 is reciprocated downwardly to a position shown in FIG. 16, allowing ameasured quantity of hot plastic to move into the opening as shown inFIG. 16. The plunger is moved to a position shown in FIG. 17, thusramming the plastic into the mold. The plunger 38 is held in thatposition for a short period. Then mold 33 is again moved upwardly to theposition shown in FIG. 18, allowing .the central portion of the plasticcontaining a foaming agent toexpand downwardly through the channel ofthe mold to form a foamed core. The plunger 38 is moved to the positionshown in FIG. 18 ready for the next cycle. After the molded part hassufiiciently hardened the mold 33 is parted and the molded articleremoved therefrom.

In the foregoing operation the relatively thin sections of the bottlecap illustrated as being made of solid plastic are cooled sufiicientlyby the mold 33 while under the pressure of the ram in the position shownin FIG. 17 that the plastic is hardened and the foaming agent in thatportion of the plastic is not effective to cause any substantialexpansion of the plastic, thus causing this portion of the molded pieceto be in a solid, substantially unfoamed, unexpanded condition. Indirectcooling means can be provided in the mold around this portion of themolded article, if desired, to assist in the cooling. The centralportion of the plastic in the mold, as shown in FIG. 17, does not becomesufiiciently cooled during the injection molding step to set up orharden, and when the mold is separated from the pluger and the opening35, the still hot, plasticized plastic containing foaming agent foamsunder the influence of the foaming agent, thus forming the cellular plugstructure illustrated.

The following examples illustrate the methods and articles made fromvarious thermoplastics, but the examples are illustrative only and arenot to be taken as limiting the invention.

Example I Low density polyethylene in particle form containingp,p'-oxybis (benzenesulfonyl hydrazide) as a foaming agent wasintroduced into a molding machine of the type of FIGURES 1 to 6 where itwas heated and plasticized to a workable condition. This foaming agenthas a decomposition range of about to C. Bottles were molded using themachine as described in the description of FIGS. 1-6. The temperature inchannel 24 and tubular cavity 23 was maintained at about 305 F. Thepressure during the step shown in FIG. 2 was theoretically about 1800p.s.i.g., although actual pressure may have been somewhat less due tofriction losses. A bottle was molded in the manner described withrespect to FIG- URES 1-6, and the resulting bottle had a cellular foamedstructure while the neck or finish was substantially solid andunexpanded.

In the cycle of operations the time of the total cycle was 31 seconds,while the time from the beginning of the cycle shown in FIG. 1 to thetime the sleeve 25 reached the position shown in FIG. 3 was 2.6 seconds.Sixty bottles were molded in this manner.

Example II The procedure described in Example I was repeated, but usinga high density linear polyethylene having a density of about 0.96gms./cm. and a melting point of about 260 F. This polyethylene contained1 percent by weight. 1,1-azobis (formamide) as the foaming agent. The.temperature in the channel 24 and the cavity 23 was maintained at about315 F. The bottle again had a substantially solid unexpanded neck orfinish portion integral with a cellular body portion.

Example III.

' The procedure of Example I was again repeated but using particulatepolystyrene containing pentane intimately dispersed therein as a foamingagent.

The temperature in the channel 24 and the cavity 23 was maintained atabout 325 .F.

The bottle so produced had a substantially solid, un-

expanded neck or finish integral with a foamed body portion of very finecelled foamed structure.

In the embodiment of the method described with respect to FIGURES 1-6and with respect to FIGURES 7-15, the step of blowing the air as inFIGURES 5 and 6 -and FIGURES 13 and 14 can be omitted where thedimensions of the foamed body of the article are not desired to begreater than produced by the step shown in *FIGURE 4 or FIGURE 10. Thetubular foamed extruded body is merely cooled in place, and can bepinched together at the end, and severed, and removed from the apparatusas a finished article.

The invention has been described as being applied to organic plasticmaterials. The terms plastic and thermoplastic, as used herein, defineany organic material which has the required condition of plasticity topermit expansion and setting in predetermined form.

The terms tubular and tubing, as used herein, are intended to includeany hollow shapes in which plastic material can be formed includingnon-circular and irregular shapes.

As will be evident to those skilled in the art, various modifications ofthis invention can be made or followed in the light of the foregoingdisclosure and discussion without departing from the spirit or scope ofthe disclosure or from the scope of the claims.

I claim:

1. A method which comprises the steps of (1) providing a single,undivided quantity of hot plasticized plastic material containing anintimately dispersed foaming or cellulating agent, ('2) forming asubstantially unexpanded, non-cellular shaped end portion of an articlefrom a first portion of said undivided quantity of plastic materialunder temperature and pressure shaping conditions which prevent anysubstantial foaming of said end portion by said foaming agent andchilling said end portion to an unplasticized essentially rigidcondition preventing foaming even at a lower pressure, (3) from a secondportion of said undivided quantity of plastic material forming thebalance of said article integral with said shaped end portion at a lowerpressure condition and a temperature condition wherein said secondportion is still plasticized, whereby said second portion of saidarticle is expanded into a cellular structure by the action of saidfoaming agent, said single quantity of plastic material remainingundivided and unseparated throughout said method.

2. A method of forming a shaped plastic article having a cellularplastic body portion integral with a substantially unexpanded,non-cellular end portion, said method comprising the steps of (1)providing a single, undivided quantity of hot plasticized plasticmaterial containing a foaming or cellulating agent, (2) moving a firstportion of said undivided quantity of plastic material into definedportions of a shaping mold under temperature and pressure conditionspreventing any substantial expansion of said first portion by saidfoaming agent and thereby forming said end portion and chilling said endportion to an unplasticized essentially rigid condition preventingfoaming even at a lower pressure, (3) shaping a second portion of saidundivided quantity of plastic material integral with said first portionat a lower pressure condition and a temperature condition wherein saidsecond portion is still plasticized, whereby said second portion becomesexpanded to a cellular form during said shaping, thereby forming saidbody portion, said single quantity of plastic material remainingundivided and unseparated throughout said method.

3. A method of forming a shaped plastic article having a cellularplastic body portion integral with a substantially unexpanded,non-cellular end portion, said method comprisingthe steps of (1)providing a single, undivided quantity of hot plasticized plasticmaterial containing a foaming or cellulating agent, (2) moving a firstportion of said undivided quantity of plastic material into definedportions of a shaping mold under temperature and pressure conditionspreventing any substantial expansion of said first portion by saidfoaming agent and chilling said end portion to an unplasticizedessentially rigid condition preventing foaming even at a lower pressure,(3) extruding a second portion of said undivided quantity of plasticmaterial integral with said first portion at a lower pressure conditionand a temperature condition wherein said second portion is stillplasticized, whereby said second portion becomes expandedto a cellularform during said extruding, thereby forming said body portion, saidsingle quantity of plastic material remaining undivided and unseparatedthroughout said method.

4. In a method of making a container having a finish portion and a bodyportion from plaslicized plastic material containing intimatelydispersed foaming agent capable of liberating a gas in said plasticizedmaterial when said material is subjected to a plasticizing temperatureand atmospheric pressure the steps of (I injection molding at least saidfinish portion of said container in a closed mold of annularcross-section at a superatmospheric pressure sufficient to substantiallyprevent foaming of said material by said agent, (2) releasing theinjection molding pressure after said injection molding step, (3 forminga blowable bubble of said plasticized material in a blow mold, (4)injecting air under pressure into said enclosed tube to inflate the tubeto the final configuration of the body portion of said container and (5)accommodating foaming of the plasticized material of said tube duringthe performance of the steps (2) through (4) above set forth.

5. In a method of making a container having a finish portidn and a bodyportion from plasticized plastic material containing an intimatelydispersed foaming agent capable of liberating a gas in said plasticizeamaterial when subjected to the temperature of said plasticized materialand atmospheric pressure, the steps of injecting plasticized materialtinder pressure into a closed mold conforming to the finish portion ofsaid container, forming additional plasticized material into a blowablebubble integral with said finish portion and at substantiallyatmospheric pressure and, while said additional material is stillplasticized, utilizing said foaming agent to liberate said gas in saidadditional p-lasticized material during said forming step to foam thematerial constituting said bubble, and blowing the foamed bubble to thefinal configuration of the body portion of said container.

6. In a method of making an article having a first, dense noncellularportion and a second, cellular portion from plasticized plastic materialcontaining intimately dispersed foaming agent capable of liberating agas in said plasticized material when said material is subjected to aplasticizing temperature and atmospheric pressure, the steps of (1)injection molding said first article portion in a closed mold at asuperatmospheric pressure suflicient to substantially prevent foaming ofsaid material by said agent, (2) chill- :ng said material sufficientlyto prevent substantial foaming thereof at atmospheric pressure, (3releasing the iniection molding pressure, (4) forming a tubular parisonfrom additional plasticized material at substantially atmospherepressure, (5 enclosing the tubular parison in a blow mold, (6) injectingair under pressure into said enclosed parison to inflate the parison tothe final configuration of the article second portion and (7)accommodating foaming of the plasticized material during the performanceof the steps (4) through (6) above set forth.

7. In a process for the production of blow molded hollow plasticarticles wherein a parison of said plastic is formed and then at least aportion of said parison is expanded within a mold to cdnform to thecontour of said mold by a fluid medium, the improvement comprisingincorporating a foaming agent into said plastic prior to formation ofsaid parison so that said portion of said parison is foamed before beingblow molded, thereby forming an at least partially foamed plasticarticle as a product of the process.

8. In a process for the production of blow molded hollow plasticarticles wherein a parison of said plastic is formed and then saidparison is expanded within a mold to conform to the contour of said moldby a fluid medium, the improvement comprising incorporating a foamingagent into said plastic prior to formation of said parison so that saidparison is foamed before being molded, thereby forming a foamed plasticarticle as a product of the process.

9. In a process for the production of blow molded hollow polyolefinarticles wherein a parison is extruded around a mandrel and then saidparison is expanded within a mold by a fluid medium, the improvementcomprising incorporating a foaming agent into said polyolefin prior toextrusion of the parison so that said parison is foamed before beingmolded, a'nd then blow molding said foamed parison, thus forming saidfoamed polyolefin hollow articles as a product of the process.

10.. The process according to claim 9 wherein said polyolefin ispolyethylene and said agent is present in the range 0.5 to about 10.0weight percent based on the total weight of said polyolefin and saidagent.

11. A process for producing a foamed plastic hollow article whichcomprises forming a mixture of a normally solid plastic and a foamingagent of the group consisting of volatile liquids and finely dividedsolids which decompose to gaseous products at extrusion temperatures,extruding said mixture through an orifice to form a parison, saidparison being foamed due to said agent, and blow molding said foamedparison within a blow mold to form said foamed article as a product ofthe process.

12. The process of claim 11 wherein the amount of said foaming agent iswithin the range of from about 0.5 to 10.0 weight percent of saidplastic and agent mixture.

13. The process of claim 12 wherein said plastic comprises essentiallypolyethylene.

14. The process of claim 10 wherein said plastic comprises essentiallypolyethylene having a density of about 0.96.

15. The process of claim 12 wherein said foaming agent comprisesp,p'-oxybis(benzene sulfonyl hydrazide).

16. A method as defined in claim 4 wherein said step (3) is carried outby extruding a tube and pinching the tube shut between the sections of aclosable blow mold.

References Cited UNITED STATES PATENTS Re. 24,734 Sherman 264-97 3:

2/ 1960 2,804,654 9/ 1957 Sherman 264-97 X 2,964,299 12/1960 Roggi et a1264-47 2,966,702 1/ 1961 Soubier 264 97 3,225,127 12/ 1965 Scott 264-542,023,905 12/ 1935 Schwab. 2,03 5,404 3 1936 Quinn. 2,150,287 3 1939Minor. 2,319,042 5/1943 De Wyk. 2,716,77 8 9/1955 Beare. 2,767,436 10/1956 Noland et a1.

2,898,632 8/1959 Irwin et al. 7 2,898,634 8/1959 Alderfer. v 2,908,94310/ 1959 Miller. 2,950,505 8/1960 Frank.

PHILIP E. ANDERSON, Primary Examiner US. Cl. X.R.

8. IN A PROCESS FOR THE PRODUCTION OF BLOW MOLDED HOLLOW PLASTICARTICLES WHEREIN A PARISON OF SAID PLASTIC IS FORMED AND THEN SAIDPARISON IS EXPANDED WITHIN A MOLD TO CONFORM TO THE CONTOUR OF SAID MOLDBY A FLUID MEDIUM, THE IMPROVEMENT COMPRISING INCORPORATING A FOAMINGAGENT INTO SAID PLASTIC PRIOR TO FORMATION OF SAID PARISON SO THAT SAIDPARSION IS FOAMED BEFORE BEING MOLDED, THEREBY FORMING A FOAMED PLASTICARTICLE AS A PRODUCT OF THE PROCESS.